There are a number of target acquisition platforms for mobile assets such as drones, aircraft, and military vehicles. In one example, the target is a military objective and a guided munition, rocket, or missile is dispatched from a mobile defense asset at the target. In embodiments, a guided projectile can be a guided munition, rocket, missile, artillery round, glide munition, or guided bomb. A rocket is a projectile/vehicle that achieves thrust from a rocket engine. A missile is a self-propelled precision-guided munition system. The guided munition may have some initial estimation of the target, but uses other mechanisms to accurately direct the guided munition to the target location. Since the delivered guided munition is destroyed on impact, there is a strong desire to provide an accurate but low cost guidance system since it is only used once. Strong motivations exist for increased targeting accuracy. This can reduce collateral damage, especially in confined areas. A component of trajectory control to achieve this accuracy is gravity bias, or Gbias. Gravity influences the guidance of projectiles by modifying the trajectory downward compared to the trajectory in the absence of gravity. Gbias compensates for the effects of gravity.
Rate based autopilots in current designs have a simplified form of Gbias that results in an inherent Gbias of 0.7 to 0.9 without any knowledge of the orientation of “Up and Down”. Inherent Gbias partially corrects for acceleration due to gravity. Since the inherent Gbias of current methods is below 1.0, the resulting trajectories at longer range are very flat, and in some cases are actually pulling up in the endgame, skimming just a few feet above the ground for many tens of meters in front of the target. The end result is a very low and flat flight trajectory during terminal guidance and high lift requirements on the airframe in the end game. In some cases the low flat trajectory shape results in ground impacts in front of the target, warhead skips and fuze malfunctions, reduced warhead effectiveness due to the proximity of a near ground impact miss, and a reduced maximum range. These previous attempts to shape the trajectory were primarily accomplished by operating with a relatively low proportional navigation gain. The low navigation gain allowed the rocket to stay higher earlier in the engagement and to pull down on the target later in the flight when inertial line-of-sight (ILOS) rate errors increased. The method was somewhat effective given the data available to the autopilot.
What is needed is a technique to reshape guidance and control trajectory to substantially extend maximum range capability as well as improve the terminal flight path angles without any negative effects when engaging short and medium range targets, increasing the probability of hit, reducing Circular Error Probability (CEP), and increasing the terminal flight path angle for increased warhead precision.